The Conservatives are on side of hard-working taxpayers, David Cameron said today as he launched his party's local election campaign.

The Tory leader said the next Conservative government would take practical steps to keep council tax down.

"Any excessive rises in council tax would have to be backed by a local referendum," Cameron said.

"Taxpayers need our help now."

Cameron told those at the launch of the Conservative party campaign in Dewsbury that wasting public money was "a slap in the face to people who live on tight budgets".

"[This is because] council tax can swallow a significant part of their disposable income. For a typical pensioner, a third of the increase in the basic state pension has been eaten up in higher council tax.

"So I'm delighted that Conservative councillors here in Kirklees are setting a good example by proposing lower tax increases for pensioners.

"As I go round the country, I'm saying to Conservative groups on local councils: please remember those people when setting your tax. We have to try to protect the public from Labour's council tax rises.

"My message is this: If you're re-elected, keep council tax down. And if you're elected for the first time, really work to find efficiency savings. Conservatives are on the side of hard-pressed taxpayers. We never forget that it's your money we're spending."

The Tory chief also used the launch to urge Londoners to back Boris Johnson if they wanted to oust Ken Livingstone as London mayor.

"Everyone knows it's a straight fight between Boris Johnson and Ken Livingstone," he said. "Between a man with the personality and policies to unite Londoners and a man who has spent more than 20 years dividing people… It would be a tremendous achievement to defeat a sitting mayor. All the indications are that it will be close. But if anyone can do it, Boris can."

Cameron insisted his Conservative party had "the new ideas and the long-term policies to make it happen".

"Every Conservative vote on May 1 will help to turn these aspirations into reality," he said.